Negative ion properties of tetracyanoquinodimethan: Electron affinity and compound states

Abstract
Bound and excited negative ion states of gaseous 7,7,8,8-tetracyanoquinodimethan (TCNQ) are studied from experiments involving collisions of electrons and fast cesium beams with TCNQ. The electron affinity of TCNQ is measured to be 2.8+0.05−0.3 eV by the collisional ionization technique. TCNQ attaches electrons with energies of ∼0, 0.7, and 1.3 eV (values represent peaks in cross section) to form long-lived compound negative ions which are metastable with respect to autodetachment. The lifetime for the decay of TCNQ−* decreases from ∼2×10−3 sec at ∼0 eV to ∼10−4 sec at ∼4 eV. Evidence for a third compound negative ion state is seen as a peak in the TCNQ− signal at ∼3.2 eV. This state is metastable with respect to autodetachment and dissociation into the products C11N3H−3+HCN0.